In the past few years, the distribution license holders are increasingly forced to reduce their operational costs. This means, that the elements of the distribution system may have to operate closer to, or even exceeding their maximum lifestyle. In order to make this possible to maintain or even improve the quality of the service they provide, it is essential to determine the current status of the network elements. This information can help them to make decisions about maintenance, repair or even replace the elements.
In recent years the growing interest in advanced diagnostic systems resulted in several diagnostic methods which can provide data, suitable for statistical analysis. The insulation diagnostics aim to uncover the existing defects and estimate the degree of the degradation, thus provide adequate information to determine whether how long the insulator may remain in operation.
The results of dielectric measurements reflect the general aging condition of the cable insulation and the PD (partial discharge) processes are able to detect the local faults. In the first part of my thesis I focus on the evaluation and the combined use of this methods.
Then I present a diagnostic procedure which is based on the physical phenomenon that partial discharges induce high frequency current to the solid cable insulation. After that I describe an algorithm which provides statistically useful data supplied by a high frequency current transformer.